Method of operating and system of control for electrical generators.



PATENTBD MAY 26', 1908.

No. 888,912. I

v B.. e. LAMME. v METHOD OP'OPERATING AND SYSTEM OF CONTROL FORELECTRICAL GENERATORS;

APPLIUATION FILED :AUG. 2.1906.

I WITNESSES:

ATTGRNEY UNITED srnrrnsrnrnivtr OFFICE.

BJZXL-illlifi t1. LAMLuii, U1 PIT'lS ilIRtL lliXN SYLVAX IA, ASSIGNOR TOWESTIN (3H1). li

Tlill? tv-llAXl'FACTlIRING t'UMlAXY. A CORPORATION OF PENNSYLVA') METHODOF OPERATING AND SYSTEM OF CONTROL FOR ELECTRICAL G-IF JERATORS.

Specification of Letters Patent.

Patented May 2b, 1 908.

Application filed August 2, 1906. Serial No. 328,870.

To all UllOTllit may concern:

Be it known that I, BENJAMIN G. LAM'M'E, a citizen of the United States,and a resident of littsburg, in the county of Allegheny and State ofPennsylvania, have invented a new and useful Improvement in Methods ofOpcrating and Systems of Control for Electrical (:enerators, of whichthe following is a specification.

.\l y invention relates to methods of operating, and to systems ofcontrol for, dynamoelectric machines having seriesconnected field magnetand armature windings.

The object of my invention is to provide a method of, and means for,causing electrical mot ors, having series-connected field magnet andarmature wimlings to operateas braking generators under stableconditions.

Electrical motors that are employed for the propulsion of railway andother vehicles are usually of the series type, and may be readilyconverted into braking generators, by reversing the connection of eitherthe field magnet or armature windings. However, if such a machine isconnected to a'braking resistance orother circuit, it may pick up verysuddenly as a generator and cause a violent shock because of theexcessive load. It, also, will not operate-as a generator under stableconditions unless'some meansis provided for maintaining thefield magnetstrength substantially constant.

According to the present invention, a stor' age battery-is connected inshunt relation to the field magnet winding before the machine isconnected to the braking circuit, so that it will begin operation as aseparately excited generator and no severe shock will result. Thestorage battery remains connected in shunt relation to the field magnetwinding during operation of the motor as a generator, and servesto"cause a substantially constant amount of currentto be supplied to thefield magnet winding, so that stable conditions of operation aremaintained.

In another application Serial No. 306,217,

filed by me March 15,4906, I have claimed broadly methods of, and meansfor, maintaining substantially constant field strength in generatorshaving series-connected field ma net and armature windings, and in thatapplication I have shown and described means for effecting the desiredresult in either direct current or alternating current motors. The meansof thepresent application is a modification of those set forth in theabove mentioned application and is especially adapted to be employed inconnection with direct current motors.

The single figure of the accompanying drawing is a diagrammatic view ofa system of control that embodies my invention.

A motor that comprises field magnet and armature windings, 1 and 2,respectively, may be supplied with current from a suitable circuit, suchas that which comprises a trolley conductor 3, and a track rail 4, andthe circuit connections and arrangements of the field magnet andarmature windings may be governed by'means of a controller thatcomprises a plurality of stationary-contact fingers .S'a'nd a pluralityof movable conducting segments 6. 7, 8, 9, 10, 11', 12, and 13 that maybe brought, in any suitable manner, into engagement with the stationarycontact lingers along the position-indicating lines a, b, e, (Z, c, andf. In operating the motor as a ,propelling means for a vehicle uponwhich it may be mounted, the controller is first moved to the positionindicated by the broken line a, whereupon the field magnet and armaturewindings, 1 and 2, become connected in series relation and in serieswith a suitabldresistance 14. The circuit thus'established is by way ofthe parts bearing reference characters 3, 6, l4, 1, 7, 2,8, and 4 and isshown dia' grammatically just below the conducting segments 6, 7, and 8.Asthe controller is moved to the succeeding positions I) and c, theresistance 14 is gradually removed from the motor circuit, therebeing-nothing novel in the manner in which circuits of the machine arecontrolled when operating as a motor.

When it is desired to operate the motor as a braking generator, thecontroller is first moved toward the positi'onindicated by the brokenline (1, whereupon a storage battery 15 becomes connected in shunt tothe field magnet Winding which is thus separately excited. When thecontroller reaches the position (1, the field magnet and armaturewindings are againd series relation, though the connection of hearmature to the field magnet is reversed, and the resistance 14 isconnected in closed circuit therewith in the usual manner. The batteryremains connected between the terminals ofthe field magnet winding toserve as a shunt therefor of substantially constant voltage and it ispreferably of a voltage equal to the drop of potential over of potentialoccurs over the field magnet the field magnet Winding under the mostusual or normal conditions of operation. When but a small amount ofcurrent is generated by the machine, and only a small drop winding byreason of the armature current that traverses it, the storage batterywill assist in supplying current to the field magnet winding and Willserve to maintain the field magnet strength at substantially its normalvalue. If the. machine generates more than the normal amount of current,the drop of potential over the field magnet Winding caused by thiscurrent will be increased above the voltage of the storage battery andthe battery will be charged by the current generated in excess of the'amount necessary to maintain the field magnet strength at substantially its normal value. Thus the field magnet strength ismaintained substantially constant.

It will, of course, be understood that the invention may be employed insystems com prising more than a single motor, the circuit arrangementsand connections of which mag be adjusted in any desired or suit ablenmnner.

I claim as my invention: 1. The method of operating a generator havingseries-connected field magnet and armature windings, which consists infirst connecting a secondary battery in shunt relation to the fieldmagnet Winding and in then connecting the generator in a brakingcircuit.

2. The combination with an electrical generator having series-connectedfield magnet and armature windings, a secondary battery and a circuit,of means for first connecting the battery in shunt to the field magnetand then connecting the generator to the circuit.

In testimony whereof, I have hereunto subscribed my name this 28th dayoi July, 1906.

lVitnesses:

()T'ro S. SCHAIRER, Bumpy lliNns.

